Congenital esotropia is the most common form of childhood strabismus. Considerable controversy exists in regard to the optimal timing of surgical correction. Current standard clinical practice is to perform surgery at six months of age or later. There is substantial evidence, however, to suggest that performing surgery at an earlier age may enhance the development of binocular vision and sustained good ocular alignment. This study is designed to answer the primary question: Do infants with congenital esotropia who have surgery at 11-18 weeks of age develop better binocular vision and have better ocular motor stability than infants who have surgery at 28-32 weeks of age? the study is a simple, randomized, controlled single-masked clinical trial intending to recruit 200 patients within one year. Infants between 11-18 weeks of age with comitant esotropia more than 40 prism diopters, not premature, and neurologically normal will be randomized to surgery at 11-18 weeks or 28-32 weeks of age. The follow up visit schedule has been established to approximate standard clinical practice, proposing a minimum number of visits. Both groups will be examined at one week and one moth after surgery, at one year of age and every six months after that for the duration of the study. The early surgery group will also be evaluated at 9 months of age. more frequent visits will be at the discretion of the investigator based on the specific case. the primary outcome is stereo acuity measured at age 4-5 years by a masked observer using the Randot 2 test and the Titmus fly test, both widely used in clinical practice. This will assure that unbiased standardized assessments of outcome will be obtained. Secondary outcomes include ocular motor alignment, associated motor abnormalities, reoperations, and fusion and suppression (measured with the Worth four-dot test at near and Bagolini lens test).